On 04.08.2016 18:51, Daniel Stone wrote:
On 4 August 2016 at 04:39, Michel Dänzer michel@daenzer.net wrote:
Patch 6 extends the ioctl with new flags, which allow userspace to explicitly specify the target vblank seqno. This can also avoid delaying flips in some cases where we are already in the target vertical blank period when the ioctl is called.
Is there open userspace for this?
Sure, referenced in patch 6:
https://cgit.freedesktop.org/~daenzer/xf86-video-ati/commit/?id=fc884a8af253...
https://cgit.freedesktop.org/~daenzer/xf86-video-amdgpu/commit/?id=b8631a9ba...
What's the behaviour vs. modeset: does the modeset request block until the last-requested flip is complete? If so, is there some kind of upper bound on the number of blank periods to wait for?
Did you read the patch? :)
The only change compared to the existing ioctl is that userspace can ask for a flip to take effect in the current vblank seqno. The code added by the patch checks for target vblank seqno > current vblank seqno + 1 and returns -EINVAL in that case. This is also documented in drm_mode.h.
Is all this tested somewhere?
Yes, I've been using it for a while on all my machines.